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Specifications of the fibre-optic cable
Source publication
Accurate and rapid detection of leaks is important for subsea oil pipelines to minimize environmental risks and operational/repair costs. Temperature-sensing optical fiber cables can provide economic, near real-time sensing of leaks in subsea oil pipeline networks. By employing optical time domain reflectometry and detecting the Brillouin scattered...
Contexts in source publication
Context 1
... 6 m length of EXCEL -SWA loose tube temperature sensing optical fiber cable was connected to the analyzer, via a length of extension cable approximately 800 m long. The specifications of the optical fiber cable are presented in Table 1 (EXCEL -SWA Figure 6a shows the initial experimental setup when heating lengths of cable from 300 to 1000 mm. Based on the results obtained, the experiment was then extended as seen in Figure 6b, to ascertain the performance of the cable with heated lengths from 10 mm to 200 mm. Figure 5a shows a water tank with dimensions 525 × 375 × 225 mm. ...
Context 2
... this should ensure that no strain is passed from the pipeline to the temperature sensing cable. However by curving the cable at small radii, as shown in Figure 3, it is possible that some strain could be induced in the glass fibers (also see Table 1 for minimum bending radii). Because each length would induce a different curvature, a baseline for each length was recorded. ...
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Citations
... The main detection means based on fiber optic sensing technology include distributed temperature sensing (DTS), distributed vibration sensing (DVS) and strain sensor. Zhao et al [6] used DTS [7][8][9][10] to identify and locate pipeline leaks successfully, but it is not applicable to micro-leakage. Wang et al [11] used DVS [12,13] for micro-leakage monitoring. ...
There are great security risks in urban natural gas transportation. Once a leak occurs, the consequences are unimaginable. At present, the accurate location of natural gas pipeline leakage is still a challenging task. In order to solve this problem, a method of leak detection and location of natural gas pipeline based on weak fiber Bragg grating (w-FBG) array micro-strain sensing technology is proposed in this paper. The field pipeline model is established, w-FBG array is applied to pipeline leakage experiment, and the pipeline leakage is detected by analyzing the change trend of micro-strain. The pipeline leakage experiments under different pressures were carried out. The experimental results show that there is a good linear relationship between the pipeline leakage pressure and the wavelength change of w-FBG, and the linearity is greater than 0.99, which is consistent with the theoretical analysis and verifies the applicability of w-FBG. According to the characteristics of micro-strain transfer in pipeline leakage process, a "abrupt change point" capturing method based on peak to peak slope and threshold judgment is proposed. The results show that the proposed algorithm can effectively detect pipeline leakage and accurately locate the leakage point, and the positioning error is about 0.5 m. Compared with the traditional method, the proposed method has higher precision.
... It causes no interference to normal pipeline operation and is capable of all-weather spatiotemporal highfrequency monitoring. Mirzaei et al [17], Madabhushi et al [18], Zhou et al [19], deHaan et al [20], Großwig et al [21], and Niklès et al [22] made significant progress in this regard, and their results confirmed the feasibility of this technology for temperature sensing. ...
Currently, there is no automatic method available to measure the height of poured concrete during concreting of underground diaphragm walls (UDWs), and the conventional manual method interrupts the operation. To address this issue, a distributed fiber-optic sensing-based method for measuring the height of poured concrete during the concreting of UDWs was developed and successfully applied to the real-time measurement of the height of poured concrete. The proposed method was verified by performing a scale mode test, wherein an acrylic circular tube was used to simulate a UDW steel cage and a temperature-sensing fiber-optic cable was laid spirally to increase the spatial resolution of measurement to 0.1 m. The temperature distribution in the tube and real-time measurements of the height of the poured concrete during concreting were obtained. The proposed method was applied to the construction of a real UDW. A total of 3360 data points representing the spatiotemporal temperature distribution in the UDW steel cage were obtained. The results indicated that the temperature of the mud in the steel cage was approximately 25–26 °C when no concreting operation was performed and that the temperature of the concrete layer increased to approximately 28–31 °C during concreting. The height of the poured concrete was the boundary representing the transition from the temperature of the mud to that of the concrete, and the measurement precision reached ±0.5 m. The measurement results obtained via the proposed method were consistent with those obtained manually using a plumb bob, thus confirming the effectiveness of the proposed method for high-precision, real-time measurement of the height of poured concrete during the concreting of UDWs.
... Many scholars have noted these problems in their studies. (Madabhushi et al., 2015) studied the accuracy of a temperature-measuring DFOS method to examine submarine pipelines in the presence of leaks and described the adverse effects of the averaging effect on the precision of the measurements. The results indicated that the lower the SR is, the greater the range of abnormal variations in the temperature data, and the less accurate the results obtained. ...
Subseabed shield tunnels are constantly subjected to erosion induced by seepage and corrosive ions and elec-trochemical effects of diffuse currents from subway traction locomotives during service, resulting in damage to the outer wall of the segment. However, the outer wall cannot be directly observed, making damage identification a challenge. In this research, an approach based on distributed fiber optic sensors (DFOSs) and information fusion is proposed to solve this issue. To monitor strain, DFOSs were installed along the circumference of the segment inner wall. The strain curvature was adopted to solve the adverse influence of the spatial resolution (SR) averaging effect in DFOSs. Using the strain and strain curvature as information sources, the strain damage probability index (SDPI) and strain curvature damage probability index (SCDPI) were developed. Based on Dempster-Shafer (D-S) evidence theory, the SDPI and SCDPI were further utilized to build basic probability assignment (BPA) functions and perform information fusion for damage identification. To validate the feasibility of this approach, model experiments were conducted. The analysis of the test data indicated that information fusion can suppress the independent features of the two information sources while emphasizing their common features. The SR averaging effect, which can cause data distortion and diminish or even mask the damage anomaly feature in strain, and multiple extrema in the strain curvature that can interfere with damage locali-zation are simultaneously eliminated. The damage identification accuracy is improved, and the damage locali-zation error for the segment outer wall can reach 0.79 cm.
... It has been widely used in pipeline safety monitoring in recent years. For instance, distributed temperature sensing (DTS) technology is used to monitor pipeline leakages [69,70] and distributed strain sensing (DSS) technology is used to monitor pipeline deformations [71][72][73]. However, they are static monitoring technologies and cannot perform the real-time and dynamic monitoring of pipelines. ...
Linear infrastructures, such as railways, tunnels, and pipelines, play essential roles in economic and social development worldwide. However, under the influence of geohazards, earthquakes, and human activities, linear infrastructures face the potential risk of damage and may not function properly. Current monitoring systems for linear infrastructures are mainly based on non-contact detection (InSAR, UAV, GNSS, etc.) and geotechnical instrumentation (extensometers, inclinometers, tiltmeters, piezometers, etc.) techniques. Regarding monitoring sensitivity, frequency, and coverage, most of these methods have some shortcomings, which make it difficult to perform the accurate, real-time, and comprehensive monitoring of linear infrastructures. Distributed acoustic sensing (DAS) is an emerging sensing technology that has rapidly developed in recent years. Due to its unique advantages in long-distance, high-density, and real-time monitoring, DAS arrays have shown broad application prospects in many fields, such as oil and gas exploration, seismic observation, and subsurface imaging. In the field of linear infrastructure monitoring, DAS has gradually attracted the attention of researchers and practitioners. In this paper, recent research and the development activities of applying DAS to monitor different types of linear infrastructures are critically reviewed. The sensing principles are briefly introduced, as well as the main features. This is followed by a summary of recent case studies and some critical problems associated with the implementation of DAS monitoring systems in the field. Finally, the challenges and future trends of this research area are presented.
... These results show that even when the surrounding temperature changes very little, the DTS technology can still sense the occurrence of leakage [12]. Using the optical time domain reflection method, Madabhushi et al and Apperl et al detected the temperature gradient at any position along the optical fiber cable attached to the oil pipeline and determined the leakage location of a submarine pipeline [13]. Apperl et al arranged temperature measuring optical cables inside the pipe to detect whether there was water intrusion through the change in temperature within the pipe [14]. ...
Determining the leakage location in an underground gas pipeline is a serious technical problem. Distributed fiber optic testing technology based on Brillouin optical frequency domain analysis (BOFDA) can be used for monitoring the change in the strain and temperature of the surrounding media caused by the gas leakage. In this study, a point source leakage model was built. The distributed fiber optic strain and actively heated fiber optic were installed around the pipeline to monitor the gas pipeline leakage. Variations in the strain and temperature characteristics of the pipeline under different gas pressure conditions were found to be in the range of -392–402 με and 3.5 ℃ during the 1.0 MPa gas leakage, respectively. When the soil model was loaded with a gas leakage pressure of 0.3–1.0 MPa, a significant variation in strain and temperature was noticed. The copper mesh actively heated fiber optic can effectively identify the location of the leak. Meanwhile, the heating rate of the actively heated fiber optic cables in different media environments were obtained and ranked from fast to slow: air, followed by general soil, followed by leakage soil. This led to the generation of new technology to detect the leakage location of buried gas pipelines through actively heated optical cables.
... Temperature is an effective tracer physical parameter that has been used to monitor tunnel fires (Aralt and Nilsen, 2009), rock and soil seepage Chen et al., 2021a;Su et al., 2017), oil pipeline leakage (Madabhushi et al., 2015), underwater concrete structure cracks (Zhu et al., 2020;Chen et al., 2021c;Zhang et al., 2021), and voids in concrete face rockfill dams (Chen et al., 2021b); reports on the use of temperature to monitor debris flows are limited. A debris flow is a complex multiphase mixture of a non-Newtonian fluid and soil . ...
Conventional devices for monitoring debris flow have the drawbacks of short service life, unreliable data transfer, and vulnerability to severe weather in the field. Currently, passive devices using fibre optical sensing techniques have been designed for monitoring debris flow; however, they only focus on debris flow events, ignoring the detection of kinetic parameters, such as the debris flow depth. Based on the heat exchange effects between debris flows and obstacles, we developed a new method using temperature sensing to detect debris flows and their flow depth. To validate this method, we performed flume tests of a debris flow to simulate a scenario of debris flow scouring obstacles. Our results showed a debris flow can significantly reduce the temperature of measuring points within its scouring range, but it barely influences the measuring points beyond the scouring range. Therefore, the mud depth can be estimated according to the distribution of the temperature drops and cooling rates at each measuring point. The cooling rate induced by air currents is much lower than that induced by debris flow, which can be used to distinguish them in practical engineering applications.
... The method is only effective for pressurized pipelines and the detection length is limited due to the high signal attenuation. The most popular method for leakage detection of pipelines (mostly for gas and oil pipelines) is the direct temperature measurement using distributed fiber optic temperature sensor located in the vicinity of the pipeline (Jacobsz and Jahnke, 2019; Madabhushi et al., 2015;Nikles, 2009;Tanimola and Hill, 2009). A temperature anomaly, either increase or drop based on the property of the transported fluid, is an indication of leakage. ...
Water pipelines are the efficient and reliable way for water transportation. Leakage of pipelines can lead to tremendous waste of water resources and large economic loss. In this paper, a novel leakage detection method was proposed based on active thermometry and fiber Bragg grating (FBG) based quasi-distributed fiber optic temperature sensing. In this method, the thermal sensing cable was fabricated by coupling heating cable with quasi-distributed temperature sensors. The heat was introduced by the heating cable and the temperature response was measured by the quasi-distributed fiber optic temperature sensor concurrently. The leakage can be detected and located by identifying the local low values in the temperature profile along the pipelines. The feasibility of the proposed method was validated by finite element simulation and experimental investigation. Good agreement between simulation and experimental study was achieved. The results confirmed the effectiveness of the proposed method for leakage detection.
... Fibre Bragg grating (FBG) sensors and distributed fibre optic (DFO) sensors have attracted a significant research attention in the last two decades in the fields of civil and mechanical engineering, in the interest of high sensitivity, long-term stability, reliability, corrosion resistance, accuracy, flexibility, and large-scale monitoring (Selker et al., 2006b, Gifford et al., 2007, Leung et al., 2015a, Madabhushi et al., 2014, Sounthararajah et al., 2017. In an appropriate fibre installation with appropriate bonding with the host structure, both DFO and FBG sensors can experience the exact strain as the host structure experiences at a strain accuracy of 5µε and 1.2 µε, respectively. ...
The paper aims to evaluate the effectiveness of both distributed fibre optics sensors (DFOs), and fibre Bragg grating sensors (FBGs) to acquire an accurate measurement of the flexural strain of foamed bitumen stabilised (FBS) beams and to assess the material behaviour under both static and dynamic loading conditions. The beams were equipped with DFOs, FBGs and a linear variable differential transformer (LVDT) to perform the static and dynamic flexural tests using a four-point bending apparatus. The initial plastic flexural strain progression of both top and bottom faces of the beam specimen under different test conditions, including different load pulse shapes and rest periods were evaluated. The results revealed that both haversine-upward and haversine-downward pulse shapes lead to a significant amount of plastic flexural strain compared to that evolved through sinusoidal pulse shapes. However, the plastic flexural strain under haversine pulse shapes can be minimised by introducing a rest period at certain cycle intervals. Further, the flexural strain profile captured by DFOs during the static and dynamic flexural tests indicated the capacity of DFOs to detect cracks initiation and propagation.
... As a very effective tracer parameter, temperature has been widely used in monitoring tunnel fire, 17,18 seepage, [19][20][21][22] and oil pipeline leakage. 23,24 Fiber optic pyrometry and temperature tracer method have been combined into an effective method to realize extensively distributed and automatic monitoring. With proper protection measures, the fiber optic temperature sensing system can be applied to harsh environments. ...
Crack detection is an important issue in the health monitoring and performance evaluation of concrete structures. Based on the heat transfer theory, a temperature tracer method and a monitoring system for crack detection in underwater concrete structures are presented in this paper. The system is composed of an integrated sensing and heating system, a monitoring tube, and multiple casing tubes. The inner diameter of the casing tube should be larger than the outer diameter of the monitoring tube so that there is a certain gap between the casing tube and the monitoring tube to form a cavity. Water fills the cavity along the crack face when the underwater concrete structure cracks, resulting in a change in the surrounding medium at the cracked site. Thus, the cooling rate of the heat source in the monitoring tube corresponding to the cracked site will be accelerated. Crack identification can be done based on a comparative analysis of the cooling curves of the heat source in the uncracked and cracked states. The effects of cavity geometry size and intensity of heat source on crack identification are studied using numerical simulations and crack detection tests. Both simulations and test results confirm the feasibility of the proposed crack detection method.
... The existing pipeline leak detection technologies are mainly divided into four categories: leak medium detection method, pipe wall parameter detection method, acoustic detection method and optical fiber distributed sensing monitoring method [4][5][6]. Negative pressure wave monitoring method has become one of the research hotspots and main technical means in the field of pipeline leakage detection in recent years due to its simple implementation and easy maintenance [7]. In the actual application process, due to the influence of signal attenuation and environmental noise, the inflection point of the negative pressure wave signal is not clear, and the system positioning accuracy is not high [8]. ...
Accurate estimate the time difference of the leakage negative pressure wave signals reached both sides of the sensor at the two sides of the leakage point is the key to accurate location of the leakage point. Based on the theoretical analysis of cross-correlation time delay estimation algorithm and characteristics of negative pressure wave signal, a cross-correlation delay estimation method for pipeline leakage negative pressure wave signal is proposed. Through wavelet transform, signal conversion and cross correlation function analysis of discrete negative pressure wave signal sequence obtained by high-speed sampling, the time difference of the negative pressure wave signal monitored by the sensors on both sides of the leakage point can be accurately obtained. In the laboratory’s 102.8 meters pipeline, leakage was simulated through the valve, the time delay estimation and leak location experiment of the sensor at the two ends of the pipeline were analyzed, and compared with the wavelet analysis method. The experimental results show under the condition that the leakage is 10%, 5% and 2% of the total pipeline volume, the cross-correlation analysis algorithm has a positioning error interval of 0.97%-1.46%, which is better than the current positioning error 0.48%-2.43% of the wavelet analysis algorithm. At the same time, it avoids the influence of different wavelet types and analysis scales in the wavelet analysis algorithm on positioning accuracy, and is more suitable for pipeline leakage monitoring system to real-time online monitoring needs, has a wide application value.
